Agglomerating method and apparatus



July 7, 1964 L. J. ERCK ETAL 3,140,326

AGGLOMERATING METHOD AND APPARATUS Original Filed Feb. 15, 1956 6Sheets-Sheet 1 FINE CONCENTPATES FROM PLANT F/L mA TE 0W5 8 00% ma/sruzzSURGE 8/ N FEEDER EEEOEE CONVEYOR CONVEYOR ADD/ 77 v55 BENTON/TE ADD/TIVE'S L IMESTONE 5M [N6 Disc BENTON/TE ETC I LINES Tom= -1 $550 fox/v4T/oA/ 57c 1 7 724 vs: slurs Wk F0)? smrr F/JP/V. BALL/N6 alsc SEEDFORMAT/01V AND FINAL BALL FORMAT/0N us: or EXTRA LIP For REZOLldCML A00/ T/O/V r BA 1 1 /N6 DISC use OF FINAL mu FORMATION 5x724 LIP F072 n aI! EEROLL +/a rm v5: arm": I ra /4" /&1 1; -su.4rr rum/Ac: 5AM COMPACT-/)2 r //4 CON VE YDE FUEL 0AL OE COAE KEROLL DPUM OE ZE'POLL DISC TRAVE/VG GPA TE SHAFT FURNACE PELLET July 7, 1964 L. J. ERCK ETALAGGLOMERATING METHOD AND APPARATUS Original Filed Feb. 15, 1956 6Sheets-Sheet 2 INVENTORS 400/: J EQCK paw/4M0 c. wazzrzz g r e/14 45 5 4ATT'O NE'YS July 7, 1964 L. J. ERCK ETAL 3,140,325

AGGLOMERATING METHOD AND APPARATUS Original Filed Feb. 15, 1956 6Sheets-Sheet 5 INVENTORS 400/5 .1 fiCK 004/450 6. 10046774 ,s' 74/04/455. JAN

' A r TOE/VEYS July 7, 1964 L. J. ERCK ETAL AGGLOMERATING METHOD ANDAPPARATUS Original Filed Feb. 15, 1956 6 Sheets-Sheet 4 INVENTORS zed/5.z /?CK,/

Arroie/ve-ys July 7, 1964 L. J. ERCK ETAL AGGLOMERATING METHOD ANDAPPARATUS Original Filed Feb. 15, 1956 noo Q @0 6 Sheets-Sheet 5INVENTORS 400/5 J, 506% DOA/440 c. V/0457Z4 g 7740/1/45 4 July 7, 1964L. J. ERCK ETAL 3,140,325

AGGLOMERATING METHOD AND APPARATUS Original Filed Feb. 15, 1956 6Sheets-Sheet 6 IN VEN TORS LOU/5 J 5am? 00/1/1440 6. wazsrrn BY M4775foaarau ATTORNEYS United States Patent M 3,140,326 AGGLOMERATING METHODAND APPARATUS Louis J. Erck, Negaunee, and Donald C. Violetta,Ishpeming, Mich., and Thomas E. Ban, Cleveland, Ohio, assignors to TheCleveland-Cliffs Iron Company Original application .Feb. 15, 1956, Ser.No. 580,423. Divided and this application Dec. 29, 1958, Ser. No.796,997

(Filed under Rule 47(a) and 35 U.S.C. 116) 11 Claims. (Cl. 264-117) Thepresent invention relates generally to the art of agglomerating offinely-divided materials and is more particularly concerned with a novelmethod of agglomerating iron ore fines to produce relatively hard anddense green balls of substantially uniform size suitable for firing andconversion thereby into blast furnace or open-hearth material, and withunique apparatus implementing that method.

The terms agglomerate, agglomerating, balling, green balls, pellets andindurated pellets are used herein in accordance with their normal andusual meanings and usages in the art. Thus, agglomerate and itsderivatives are generic expressions which mean and includes all types ofbodies artificially produced from comminuted particles. Balling refersto processes of producing agglomerates by rolling comminuted materialstogether with a suitable binder. Green balls are a specific type ofagglomerates produced by balling operation. Pellets and induratedpellets results from the firing of green balls at temperaturessuificiently high that substantial strength and shock resistance areimparted to the ball products due to chemical and/ or physical changesin these products.

One essential step in the recovery of iron from horizontal ores, such astaconites and jaspers, is the conversion of the finely-divided particlesof iron ore into form suitable for charging into an open-hearth or blastfurnace. According to commercial procedures Which have been evolved forthis purpose, the iron-rich particles of specular ores are separatedfrom associated siliceous gangues by processes which leave the ironvalues in dust-like form. It has been proposed to convert these valuesinto cold compacts such as briquettes or extrusions or into induratedproducts such as pellets, sinter or nodules. A practical means foraccomplishing this result involves the pelletizing of these materials byrolling them and firing the resulting agglomerates to produce thephysical properties necessary to see these bodies through handling,shipping, charging and smelting operations. The preferred procedure andapparatus for carrying out the firing phase of this production,particularly when the ores are largely non-magnetic, is that describedand claimed in copending application Serial No. 587,393, filed by LouisI. Erck, Donald C. Violetta and Thomas E. Ban.

The agglomerating procedure and apparatus with which this invention isparticularly concerned has evolved in the art to the point where it hasbecome standard practice to employ an inclined balling drum withappropriate means for delivering fines and compounding solid materialsinto one end of the drum together with or separately from moisture toaid in the agglomeration. When conditions are proper, ball-likeagglomerates are formed as the drum is rotated on its longitudinal axisand are gradually moved toward the lower end of the drum and dischargedtherefrom and then screened and selected as to size for firing. A numberof variations in basic drum design have been developed in efforts tominimize the shortcomings of the best prior equipment, and a number ofdiiferent devices have been used in efforts to control conditions in thedrum and improve the yields of the desired agglomerates. Also, therehave been a wide variety of combinations of ingredients developed toproduce green is es s:

3,140,326 Patented July 7, 1964 balls which will have sufficientstrength to withstand the screening and handling operations leading upto firing. To the best of our knowledge, the best practices heretoforeknown along these lines are disclosed and claimed in the copendingapplication Serial No. 346,786, filed April 3, 1953, by Grover J. Holtand Louis J. Erck, now Patent 2,799,572 and in copending applicationSerial No. 587,393, filed by Louis I. Erck, Donald C. Violetta andThomas E. Ban and now Patent 3,024,101.

However, green ball production, despite these major advances, has notheretofore been generally considered to be beyond substantial advanceand improvement, particularly in respect to yields and rates. Otherdeficiencies include excessive breakage of green balls in the ballingvessels, delayed response of the balling process to corrective measuresapplied to feeding operations, and erratic control. Furthermore, inheretofore conventional equipment, irregularities calling for theexercise of control and the imposition of corrective measures aredifficult to detect because of the masking effect of the circulatingload.

In a prior art effort to improve the operation of green ball productionequipment and yield of green balls, a scraper bar was proposed. Theobject of this bar element was to establish and maintain a smooth andeven surface on the coating of fines on the inside of the balling vesselso that ball accretion would occur gradually and at a regular rate.However, the resulting substantial elimination of friction between thegreen balls and the surface on which they were supported in the vesselprecluded the realization of this general objective and lead toward theopposite result, i.e., the breakage and degradation of the green ballsdue to impact resulting when these balls slipped across the smoothsupporting surface, hitting other balls or an abutment within thevessel. Actually, under minimum fricton conditions slippage of the fineswill prevent balling altogether.

Another prior art effort involving the use of the scraper bar failed toimprove balling operations although the scraper bar was used in such away as not to provide the aforesaid smooth even surface characteristics.In this instance, the formation of green balls and the accretion of themcould not be satisfactorily carried out despite the face that thebreakage and degradation of the green balls due to impacts was therebysubstantially eliminated.

We have discovered that the rate of green ball protection can beincreased to a surprising extent by departing from the heretofore knownpractice of agglomerate production involving the use of a single drumapparatus. We have also found that this result can be obtained withoutin any way sacrificing the quality of the green balls whilesubstantially increasing yields. Furthermore, we have found that theseresults can be secured while reducing labor costs by about 50%,eliminating heretofore essential auxiliary classification equipment andsubstantially reducing power and space requirements. More specifically,We have discovered that centrifugal force and peripheral speed effectscan be controlled under certain circumstances so that green balls can beformed and separately rerolled in a single device having radially-spacedprocessing zones. Also, we have found that it is possible to carry outballing operations on a commercial scale and at high feed rates withouteither excessive green ball breakage or entrainment of fines andundersize material in the discharge from the vessel. In fact,classification as to size in accordance with our discovery can besurprisingly sharp and, moreover, may be adjusted for any predeterminedgreen ball size desired. Still further, we have found that undersizegreen balls and fines intentionally or inadvertently discharged from theprimary vessel or zone can be automatically and continuously collectedand returned for nucleation or accretion and ultimate discharge in thedesired form. Additionally, we have discovered that the resultsunsuccessfully sought by those who proposed the scraper bar and the useand control of moisture with fine materials for balling can now beconsistently obtained by combining these and other features in a certaincritical manner. A further important discovery we have made is that thevalue of a green ball, i.e., the proportion of iron ore in a green ball,can be materially increased over that hitherto obtainable with a givengrade of iron ore fines without adversely affecting the physicalcharacteristics of the ball and without increasing the cost of theballing operation by a tenth of the corresponding amount.

On the basis of these discoveries, we have invented a process and anapparatus which are new and hitherto unknown in operations of thisgeneral type. In putting into operation the present novel process andapparatus, we have found that important advantages in addition to thoseset out above can be obtained, some of them for the first time inagglomeration operations of this type and others for the first time incombination with each other.

For one thing, classification as to green ball size is substantiallyimproved in accordance with this invention and superior firing bedcondition, particularly as to back pressures, are thus more readilyestablished. Furthermore, this result is obtained through theelimination of heretofore essential equipment, i.e., by means of asingle element instead of the conventional drum, screen and conveyorcombination previously necessary for recycling undersize material. Stillfurther, green balls made according to our present method and by thisnovel apparatus have uniformly smooth surfaces which represent the idealcondition because of gas flow characteristics in green ball beds duringfiring. v

The method of this invention is applicable generally to commercialballing operations and comprises the steps of rolling together in aprimary balling zone moistened, finely-divided material, separating andremoving green balls of predetermined size from fines and smaller greenballs in the said primary zone, moving the thus separated green ballsthrough an intermediate non-balling zone, rolling the thus removed greenballs together with moistened fines in a secondary balling zone, andfinally separating and removing green balls of the ultimate desired zonefrom fines and smaller green balls in said secondary zone. Preferably,this process is carried out commercially in a continuous manner ratherthan batchwise, the several steps being conducted continuously andsimultaneously with new fines being fed into the balling vessel at arate corresponding to the rate of discharge of the fines in the form offinished green balls, due regard being had for the limits imposed onfeed rates by the capacity of the disc and green ball diameterrequirements. It will, however, be understood that this process may becarried out in a manner such that some of the steps are operatedintermittently as, for example, in the separating and removing ofagglomerates of predetermined size from the separate zones of thevessels employed in the operation. Furthermore, agglomerating inaccordance with this invention may be carried out on an essentiallycontinuous basis even though, in fact, all the steps generally describedabove are conducted intermittently. Also, it is preferable in practicingthis method to remove undersize green balls from the secondary ballingvessel or zone and to return them to the primary vessel or zone; and,for best results, this should be done on a more or less continuous basiseven when the equipment used is such that discharge of undersizematerial from the primary zone or vessel is not excessive.

As we have operated the process of our present invention to advantage,We have carried out steps in addition to those set forth above with theobjective of applying to the full-size green balls a coating offinely-divided fuel to aid in the firing of these masses to convert theminto indurated pellets as described in detail in our aforesaid copendingapplication Serial No. 587,393. Alternatively 4 or additionally, fuelmay be incorporated within the green balls suitably by adding fines ofcoal or coke breeze inballing zones. This latter practice may proveadvantageous when fines of magnetite are being balled or where a clinkeror cluster product is desired for use as openhearth furnace feed orcharge.

Briefly described in its broad apparatus aspect, the

present invention comprises a device for carrying out the abovedescribed method in which an inner, hollow cylin-- drical member isprovided as a primary balling chamber which is adapted to be mounted forrotation with its axis at an acute angle to the horizontal. In apreferred form, the device includes an annular abutment portion whichslopes relative to the base and to the side wall of the cylinder andmerges with the inside surfaces of said base and side wall to preventstatic packing of finely-divided materials while the vessel is rotatingduring balling operations. Alternatively or additionally, this devicewill include a generally cylindrical outer member of enlarged diameterwhich defines with the inner member an annular space adjacent to theouter end of the inner member constituting a secondary balling chamber.In this form, a radially-extending projection is disposed between theinner and outer members, serving as an end or bottom wall of thesecondary chamber. As a modification, additional outer members andbottom walls may be provided to multiply the balling chambers.

Referring to the drawings accompanying and forming a part of thisspecification:

FIGURE 1 is a flow sheet which illustrates the part played by the methodand apparatus of this invention in a commercial iron ore processing andpelletizing operation;

FIGURE 2 is an elevational sectional view, partly diagrammatic, ofapparatus carrying out the method of this invention;

FIGURE 3 is an elevational sectional view of apparatus embodying thepresent invention for carrying out the method described above;

FIGURE 4 is a view similar to FIGURE 3 of another type of apparatusembodying the present invention;

FIGURE 5 is a front elevational view of the agglomerating device similarto that illustrated in FIGURE 4, showing the pattern of agglomeratetravel as the device is operated to carry out the aforesaid method;

FIGURE 6 is an enlarged fragmentary sectional view of the inner end of aportion of the agglomerating vessels illustrated in FIGURE 2;

FIGURE 7 is a fragmentary, transverse, sectional view of another ballingapparatus embodying the present invention;

FIGURE 8 is a view looking into the open end of the apparatus of FIGURE7;

FIGURE 9 is an enlarged, fragmentary, sectional view of the FIGURE 7device, showing the surface trimming and conditioning means in positionwithin the balling vessel;

FIGURE 10 is a diagrammatic view illustrating the flow patterns of greenballs and fines between the several zones within the balling vessel;

FIGURE 11 is a fragmentary, isometric view of the balling disc of FIGURE7, illustrating the flow patterns of the materials in the disc duringthe balling operation;

FIGURE 12 is a perspective view of another form of balling device ofthis invention;

FIGURE 13 is a view taken on line 13-13 of FIGURE 12 showing conveyormeans and lining dressing means;

FIGURE 14 is a vertical sectional view of still another type of deviceof this invention;

FIGURE 15 is a fragmentary, sectional vertical view of another ballingdevice of this invention; and,

FIGURE 16 is a view similar to FIGURE 15 of another balling deviceembodying this invention.

The apparatus illustrated in FIGURE 2 comprises a hollow, shallow,cylindrical body 10 which is mounted for rotation on its axis on anangle of about 60 on a bearing 11 carried by a pedestal 12. A driveshaft 13 extends axially of the vessel from the lower portion thereofthrough bearing 11 and is provided with a gear 14 for driving engagementwith suitable motor and power transmissionmeans (notshown). A screwconveyor 15 is disposed with its inner end in the upper portion ofvessel 10 fordelivery of finely-divided iron ore or the like into thevessel during balling operations. A water spray is directed into the.vessel by means of a line. 17 which is connected to a suitable sourceof water under pressure (not shown). Under ideal operating circumstancesit will not be necessary to use line 17, as water delivery intothislballing machine would be by the fines themselves. When the fines,as filter cake, are delivered into this machine. they may not normallycontain sufficient moisture for ball nucleation (9 /2 moisturerepresenting the optimum condition) because of evaporation elfects andfiuctuations infilter operation. Furthermore, it will be understood thatthe position of the spray with respect to the vessel may be varied fromthat illustrated and that. the best spray position under one set ofconditions will not necessarily represent the best situation underanother set of conditions.

Green balls 18 of predetermined size are formed in vessel 10 asit isoperating, being rotated continuously at a regulated rate, and aredischarged over the lip of the vessel onto an endless belt conveyor 20for transfer to a secondsaucer-like vessel 21. Vessel 21, like vessel10, is mounted for rotation on its axis at an angle'to the horizontal,being carried by its shaft 22 in bearing 23 supported on pedestal 24,and isprovided with driving gear 25 keyed to shaft 22 and is operativelyassociated with driving means (not shown) Green balls of predeterminedsize are formed in vessel 21 as it is rotated and are substantiallycontinuously discharged over the lower lip portion of the vessel, asshown, and transported by an endless conveyor belt 28 to a third vessel30 where these green balls are rolled together with coal or coke breezeto provide a finishedcoat of fuel in accordance with the method of thisinvention as described above. Vessel 30 is suitably of the sameconstructionas vessels 10 and'21 and is driven in the same manner andwith its axis at an angle to the horizontal in accordance with thepreference of the operator and the thickness of the fuel coatingdesiredon the green ball product. A screw conveyor 31, suitably of constructionand motor operation substantially like conveyor 15, is provided for thedelivery of fuel into vessel 30, the inner end of the conveyor beingdisposed in relation to vessel 30 in generally the manner of con veyor15 and vessel 10, just described above. Finished, fuel-coated greenballs rolling over the lower lip portion of vessel 30 are intercepted byan endless belt conveyor 34 and carried thereby to a suitable storagepoint or a traveling grate or other firing apparatus, as desired.

As shown in FIGURE 6, the Vessel 10 incorporates a novel feature in theform of an annular abutment portion 38 which provides a surface ofgenerally hyperbolic, concave form in transverse cross-section.Abutme'nt38 fills the corner defined by base 39 and'side wall 40 of thevessel, promotesfree rolling of agglomerates and fines and serves toprevent static packing and lumping of the finelydivided materialdelivered into the vessel by conveyor 15 and crushing of green balls. Inthe embodiment illustrated herein, abutment 38 comprises wire mesh orscreen which has been disposed across into the corner portion of thevessel and shaped to provide the curved section mentioned above. A massor bed of suitable cementitious material such as a sodium silicate,Portland cement or moist ore fines is provided under screen to providesupport for it and maintain the desired conformation in abutment 38.However, whether this abutment member is of cemented or' other material,or is actually formed in the Vessel metal itself, it will be effectiveto promote free rolling and to prevent tucking of small fragile seedsand flocs into a deep corner space where crushing compressive stressesor loads may be exerted upon them. Another advantage and function ofthis abutment element is to promote or permit the release offinely-divided material and fragile seeds and does in the to sector ofvessel rotation, as illustrated in FIGURE 5. This, in turn, results inrelieving impingement on the stationary cutter at 100 so that the smallseeds are not degraded through cutter action to an excessive degree. Thegeneral location of a cutter element in the vessel 10 is indicated inFIGURE 5 which will subsequently be described in detail, the cutterbeing eliminated from FIGURE 2 in the interests of clarity.

The balling apparatus of this invention shown in FIG- URE 3 comprises acylindrical vessel 44 of depth approximately twice that of vessels 10and 21, providing a primary balling chamber. A cylindrical outer member45 of enlarged diameter is secured to cylinder 44 toward the outer orupper end of the side walls of cylinder 44 and cooperates with thelatter cylinder to define an annular space 46 adjacent to andsurrounding the outer end of cylinder 44 and constituting a secondaryballing chamber. The side wall of member 45 extends upwardly oroutwardly beyond the open end of vessel 44 so that green balls ofpredetermined size are caught in member 45 on rolling over the outer lipof cylinder 44.

Cylindrical members 44 and 45 are provided with an annular abutment 49and 50 of curved surface so that instead of having the usual cornerpocket at the intersec tion of the base and side wall, this cylinderoffers smooth contours between the inner surfaces of the side walls andthe inner surfaces of the bottom or base elements. The purpose andfunction of this abutment member is essentially the same as that ofabutment 38 of FIGURES 2 and 6, as described above; However, in thisinstance, the abutment member'is integral part of the cylindrical body,being formed in the metal of the member.

Green balls 48 processed in chamber 46 are gradually Worked toward thelip of member 45 and are discharged from ring 45 when they have beendeveloped to a predetermined size. This discharge 51 is intercepted onleaving cylindrical member 45 by an endless belt conveyor 52 by means ofwhich it is carried to a collection or storage point 53.

The mounting and driving means for the apparatus of FIGURE 3 comprisingvessel 44 and ring member 45 is suitably essentially the same as thatdescribed in reference to the FIGURE 2 agglomerating vessels. Thus, adrive shaft 55 is mounted coaxially of vessel 44 and member 45 andsecured to the base of the vessel assembly ex tending downwardlytherefrom and being journalled in bearing 56 supported on pedestal 57.The lower end of shaft 55 is provided with driving gear 58 for operativeassociation with suitable conventional driving means (not shown) wherebyvessel 44 and member 45 are rotated on their common axis at a rateaccording to the nature of the feed material, the rate of feed delivery,the size of the green balls desired, and similar factors.

Ore fines are delivered into the primary and secondary chambers ofvessel 44 by means of two conventional feed assemblies indicated at 60and 61, the rate of feed delivery being regulated according to theoperating conditions and the capacity of the equipment, suitable drivemeans (not shown) being provided for this purpose. Moisture in the formof water sprays is delivered into both said balling chambers by meansindicated at 62 and 63.

In the apparatus of FIGURE 4, a vessel 65 having two concentric chambersis provided for carrying out the meth od of this invention. Thus,thisvessel is of generally cylindrical form having a base 66 and a sidewall 67 and open upper end from which green balls are discharged. Anannular, step-like abutment 69 is provided within vessel 65, dividingthe vessel into an inner nucleating or primary balling chamber 70 and anouter or secondary balling chamber 71, green balls 72 of predeterminedsize being discharged from chamber 70 over the edge 73 of abutment 69into chamber 71 as the vessel is rotated. Chambers or zones 70 and 71are spaced apart radially and axially and an intermediate, non-ballingzone in the form of edge 73 and adjacent portions of vessel 65 isdisposed between them. A conic section 75 of dead plate is mounted inchamber 70 in abutting relation to the riser portion of step 69 and theinner surface of base 66. A similar conic section 76 which isnecessarily of larger diameter than section 75 is provided in chamber 71abutting the tread portion of step 69 and the adjacent inner surface ofthe side wall 67. Again, the purpose of these sections 75 and 76 arethose of abutments 38 and 49 as described in: detail above.

The steps defining the separate balling zones are of dimensions suchthat the retention time in each zone is near the optimum for theparticular material to be balled in the vessel. By way of illustration,we have found that in producing green balls from iron ore fines, goodresults can be consistently obtained when the lip depth is six inchesand the disc diameter is three feet. Likewise, the depth of the lip maybe as great as nine and one-half inches when the disc is four andone-half feet in diameter. Smaller or shorter lips will also besatisfactory but larger or higher ones are not desirable.

Vessel 65 is mounted for rotation on its axis at an angle to thehorizontal by means of an axial shaft 82 attached to base 66 andextending downwardly therefrom for supporting engagement with a pedestal83. The shaft is carried by the pedestal in adjustable relation so thatvessel 65 may be turned at any desired angle to regulate the size ofgreen balls discharged from chambers 70 and 71 in accordance with thefactors and conditions governing the action of this apparatus incarrying out the method of this invention as will be subsequentlydescribed. Angular adjustment of the vessel may be accomplished by meansof a hydraulic or pneumatic piston cylinder assembly indicated at 84,piston rod 85 being connected to the lower free end of shaft 82 belowpivot point 83.

Driving means for revolving the vessel on its axis is indicated at 86 asmotor means and a V-belt drive and a ring gear 87 mounted on base 66.

The delivery of ore fines or similar material into vessel 65 andparticularly into chamber 70 is accomplished by means of a screwconveyor 88 driven by any suitable conventional means (not shown). Waterin the form of a spray is delivered into chamber 70 in accordance withthe requirements of the method of this invention by means of a line 90.

An endless belt conveyor 93 is provided to receive the green balls 94discharged from vessel 65 over the lip of side wall 67 carrying them toa point of storage or to a traveling grate or other apparatus for firingor further processing.

For the purpose of dressing and conditioning the inner surface of theportion of base 66 within chamber 70, an oscillating trimming anddressing bar 95 is disposed with its end portion 96 adjacent to the saidbase surface. By means of a lever 97 and drive means (not shown) coupledto lever 97, bar 95 is driven continuously during the period of use ofvessel 65 in balling operations. Unlike the scraper bar of the prior artmentioned above, bar 95 is not used in accordance with our invention insuch a way that an undesirable, smooth, even surface is produced in theballing zones. Instead, this bar assures the maintenance of anunpolished surface on the coating of moist fines in the vessel topromote snowball-like growth of green balls.

As shown in FIGURE 5, a stationary trimming and dressing bar 100 and asecond similar bar 101 are provided in chambers 70 and 71, respectively.Bar 100 is located at about 50 or one oclock adjacent to the outerperiphery of chamber 70 for trimming and conditioning the vessel coatingsurface in the area of abutment 75.

Bar 101 extends entirely across chamber 71 at about 130 to intercept anygreen balls and fines carried too high by rotational motion of vessel 65and thus return them to chamber for further growth, as will bedescribed.

The apparatus of FIGURES 4 and 5 is operated continuously by feeding ashredded concentrate in water mixture into the rim at about 350 whenvessel 65 is being rotated in a clockwise direction. The feed materialtends to tuck under cascading seeds of various sizes and is liftedaround the periphery of chamber 70 without tumbling to about where thematerial breaks loose from the periphery and is projected by gravity andfriction across the clean surface of the vessel base in a directionconcurrent and lateral to the vessel motion, but at a greater velocity.Small flocculated masses tend to form small spherical seeds during thisinitial fall as a result of vessel motion, and these new seeds fall uponnew layers of feed and they are statically transported to about 120. Atthat point, they are projected across the vessel deck or base surfacewith less horizontal displacement than the new feed. These smallspherical seeds are enlarged through accretion of fresh adherent feed inthis second tumble, and these enlarged seeds fall on the newer seeds andarrive in a shear zone of uplifting and tumbling masses. Random motionprevails in the shearing zone and enlarged seeds are subjected toattrition whereby the larger seeds grow at the expense of smaller oneswhich tend to seek their own specific orbit. The larger seeds tend tomigrate to the top of the tumbling masses and cascade on the surface inrelatively small generally elliptical orbits so that these green ballsnuclei are raised near the periphery and tumbled on the base surfacenear the edge of chamber 70. Eventually, when the green balls havereached predetermined proportions, they overflow the rim dividingchamber 70 from chamber 71 at a zone of emergence between 180 and 270.This overflow is the result of a displacement action exerted by new feedand by the rotary motion of the balling vessel. The green balls thusoverfiowed are cascaded in a sausage-shaped orbit in chamber 71, and arefurther enlarged through pick-up of finelydivided material whichsurprisingly preferentially adheres to the surface of the tumbling greenballs rather than nucleating into individual agglomerates of smallersize. Incoming green balls cause tumbling larger green balls to berejected by displacement from chamber 71 in a zone of emergence of about225.

The apparatus illustrated in FIGURES 7 to 11, inclusive, generallyresembles the devices of FIGURES 4 and 5, differing therefrom in thedetails of construction of the balling vessel itself. The drive meansand auxiliary equipment may suitably be essentially the same in bothcases. Vessel 105 is generally cylindrical and relatively shallow and,like vessel 65, in use is mounted for rotation on its axis disposed atan angle between about 20 and about 70 to the horizontal, depending uponthe nature of the fine material to be processed. A series of annularsteps which define three separate balling zones and a reroll zone forthe formation and progressive growth of green balls and for finalrerolling of these balls to apply thereto a suitable coating of fine oreof low moisture content or fuel to facilitate subsequent firingoperations. These steps or zones are arranged concentrically, theinnermost zone 107 being for nucleation, green ball nuclei being formedtherein by the action of the balling vessel rotating on its axis tocascade fine material continuously over a condition surface 109 ofcompacted fines covering the interior of the vessel in this zone. Asecondary balling zone 110 is adjacent zone 107, while a third ballingzone 111 is disposed outwardly of zone 110 and adjacent thereto. Zone110 is provided with a layer 112 of compacted fines which is acontinuation of layer 109, zone 107 and the inner surface of the vesselportion defining zone 111 is similarly coated with a layer 113 ofcompacted fines. Zones 107, 110 and 111 are separated by intermediatenon-balling areas or zones 115 and 116, re-

9 spectively, these being the edge portions of the annular steps overwhich the nuclei and green balls travel in their progressive movementradially and axially outwardly from the innermost zone of the vessel.

The coating of compacted fines extending over the inner surface ofvessel 105 from the innermost part thereof to the reroll section ismaintained in condition to promote formation and growth of green ballsby means of a stationary bar 120 disposed at 12 oclock, as indicated inFIG- URE 8. Bar 120 is contoured to provide a uniform, relatively smallgap whereby the thickness of the layer of fines is regulated. Control ofthe critical feature of surface condition is also obtained by means ofan oscillating trimming device 122 disposed within zone 107. The actionof these two coating-conditioning devices is such that coatings areestablished and maintained throughout the balling operations whichafford sufiicient frictional contact for fines, nuclei and green ballsthat regular and rapid green ball growth is consistently obtained.

Another critical factor in the production of green balls of the desiredcharacteristics set forth above is the moisture content of the finematerials undergoing treatment in vessel 105. Filter cake finescontaining about 8% to about 11% moisture are introduced into vessel 105by means of screw conveyors 124 and 125, serving zone 107 and zone 110,respectively. When the moisture content of these fines is less than theoptimum for nucleation of green balls or green ball growth, adequatemoisture is introduced into zones 107 and 110 by means of water spraysdelivered through lines 127 and 128, respectively. Preferably, theseintroductions of fine materials into zones 107 and 110 are continuouslyand at regulated rates in accordance with the rate of green ballformation and growth so that not only the size of the green ballsproduced is closely controlled but also the rate of that production ismaintained at a maximum.

An annular flange 130 is formed in vessel 105 to divide balling chamber111 from reroll chamber 132 and thereby prevent flow of finely dividedfuel from the reroll chamber into the balling zones.

Conveyor 125 should always deliver filter cake to the disc at a moisturecontent of 8 to 11%, but conveyor 125 may deliver filter cake that has amoisture content of 8 to 11%, but we have found it advantageous to addfilter cake with a moisture content of 4-6%. This would allow conveyor135 to add powdered fuel to the green pellets. If internal fuel isadded, this step would be eliminated.

In the operation of this FIGURE 7 apparatus, finelydivided iron ore,suitably of moisture content between about 8% and 11%, is introducedinto zone 107 and zone 110 and by action of trimming and conditioningmeans 120 and 122, a coating of compacted and finely divided material isestablished on the inner surface of vessel 105 in the balling zones.Moisture is added as required in the form of water sprays by lines 127and/ or 128 in order to produce the optimum surface condition for ballformation and growth.

As vessel 105 is continuously rotated on its axis and feeding of finesinto zones 107 and 111 continues, green ball nuclei produced in zone 107are displaced as they grow in size by fresh feed material and are movedinto zone 110 through the first intermediate non-balling zone dividingzones 107 and 110. Depending upon the operational characteristics ofvessel 105, such as the rate of rotation, the rate of feed and the rateof nucleation, a smaller or larger amount of fine material may flowtogether with greenballnuclei and small green balls into zone 110. Therate of feed of fines by conveyor 125 is adjusted according to carryoverof fines into zone 110 and according to the rate at which finely-dividedmaterial flows back into zone 107 from zone 110, as indicated in FIGURE10.

Displacement of balls of larger size occurs in zone 110 as feedthereinto continues via zone 107 and conveyor 125. These larger ballsare moved through the second intermediate non-balling zone and receivedin outer balling zone 111 where their accretion continues until they areof the final desired size and are displaced by smaller size materialfalling into zone 111 from zone 110. Again finely-divided material invarying amounts will accompany flow of displaced green balls from zoneto zone 111 and there will be a back flow of this finely dividedmaterial into zone 110, as indicated in FIG- URE 10.

Balls of the finally desired size displaced from zone 111 are caught inreroll zone 132 and by virtue of the fact that their surfaces are moist,they are readily coated with relatively dry finely-divided material asthey are rolled in zone 132 through the continued rotation of vessel105. This ball coating operation in accordance with our discovery, doesnot require fines of the relatively high moisture content essential tosuccessful green ball nucleation and growth. For this reason and becauseit is highly desirable to establish the highest possible ironvalue-moisture ratio in finished green ball products, fines areprevented, in accordance with this invention, from carrying over to anymaterial degree from zone 111 to the reroll zone and essentially theonly fine material in the reroll zone is the 4% to 6% moisture contentiron ore delivered by conveyor 135. Finished and coated green balls aredisplaced from the vessel by continued flow of green balls from zone 111and additions of material by means of conveyor 135. To insure goodrerolling results, vessel 105 is equipped with a radially-disposedstationary scraper bar 137 located in reroll zone 132 at 10 oclock. Bar137 maintains a surface in reroll zone 132 which is conductive to goodtumbling action of both green balls and powdered material, but unlikebar is not effective to return fines and undersize balls to inner zonesfor agglomeration or further growth.

Vessel 140 of FIGURE 12 is in the form of a truncated cone and is closedat its smaller end by wall or floor 141 and open at its larger end 142Where a lip 143 is provided. Vessel 140 is mounted for rotation on itsaxis with end 142 directed upwardly, said axis being disposed at anangle to the horizontal, depending upon the material to be processed,the size of the ball products to be formed in this vessel, the rate ofrotation of the vessel and similar factors. An annular body 145 issituated coaxially in vessel 140, constituting an axially extending damwhich serves to divide the vessel into an inner balling zone 148 and anouter rerolling zone 149. This dam prevents overflow of relatively moistfines into the rerolling zone. A trimming and conditioning meanscomprising an endwise reciprocating bar 150 is disposed in vessel 140 inspaced relation to opposed side and bottom wall portions of the vesselto dress the surface of the coatings of compacted fines on the interiorof the vessel and thus promote green ball formation and growth, asdescribed above. A conveyor 152 serves to deliver fine material intoZone 148 for balling, requisite moisture being provided in anyconvenient manner.

As indicated in FIGURE 12, when vessel 140 is rotated on its axis bysuitable means such as described in reference to FIGURES4 and 5,finely-divided material ball nuclei and small and large green balls aremoved about in the vessel with the result that the larger green balls,upon reaching predetermined size, are discharged by dis-' placement fromthe balling zone of the vessel over dam 145 into reroll zone 149. Acharacteristic of this device is the progressive travel of nuclei andgreen balls axi ally and radially outwardly of the vessel as thesenuclei and balls grow in size. Another characteristic of this apparatusis the fiow of a portion of fine material with the nuclei and greenballs from the inner portion of the vessel toward the dam and thecounterflow of fines from outer portions of the balling zone towardinner portions thereof. Stillanother feature of this device is the sharpseparation which is effected between the green balls of predetermineddesired size and smaller balls and fines in the discharge from theballing zone.

Vessel 160 illustrated in FIGURE 14 is generally bowl shaped, having aconcave, arcuately-formed inner surface 161. Vessel 160 is disposed onsuitable mounting means and connected to driving means of the typeillustrated in FIGURES 4 and 5, the axis of vessel 160 being at agreater or lesser acute angle to the horizontal, depending upon theconditions under which balling is to be carried out. An annular-dam 165is formed within the vessel 160 adjacent to its outer end to divide thevessel interior into an inner balling zone and an outer reroll zone.Within the balling zone of the vessel, a reciprocating bar 167 ismounted in spaced relation to the surface of the vessel and is contouredto provide a substantially uniform gap to effect trimming andconditioning of a layer of compacted and finely-divided material wherebyball formation and growth is promoted in the operation of the vessel.Green balls are discharged from vessel 160 over lip '168 asfinely-divided iron ore of requisite moisture content is introduced intothe balling zone by means of a conveyor 170 and make-up water isprovided in the form of a spray when additional moisture is required forball nucleation and growth. Fines of relatively low moisture content areintroduced into the reroll zone by conveyor means (not'shown) to providethrough the action of the balling vessel a finished coating of iron oreor fuel on the green balls discharged from the balling zone.

Operation of vessel 160 is similar to that of vessel 140 in that thecharacteristics described with reference to vessel 140 are likewiseinherent in vessel 160. Thus, following the establishment of a layer ofcoating of'comlpacted fines on the surface of the balling zone, part ofvessel 160, balling is rapidly carried out continuously with the rate ofrotation of the vessel on its axis and the rate of feed of fines andmoisture in the balling zone and relatively dry fines in reroll zonebeing regulated'for the consistent production of'the desired results.

Ball disc 178 illustrated in FIGURE is of shallow, generally cylindricalform, having an end wall 179 and a short side wall or flange portion-180. Three concentrically disposed rings 181, 182 and 183 are providedto divide the interior of vessel 178 into separate zones, the ringsbeing welded to end wall 179 in spaced relation to each other accordingto their heights. Thus, an inner nucleation zone 185 is provided,finely-divided moist material being delivered therein and subjected tothe rotary motion of vessel 178 as it is turned on its axis to causefine particles to agglomerate as described above. Nuclei and small greenballs formed in zone 185 are displaced over dam 181, being received inballing zone 187 where they are rolled together with additional finematerial, resulting in further growth. Green balls of predetermined sizeare selectively displaced from zone 187,'flowing over ring 182 intoanother balling zone 188 where further accretion of-these balls mayoccur. Displacement of green balls of predetermined desired size fromzone 188 results in these balls being collected in the outermost orreroll zone 189 which is defined by ring 183 and flange 180 of thevessel. Discharge of the finished green balls from the vessel isaccomplished by displacement of these balls from reroll zone 189 and isregulated by controlling the rate of displacement of the products frominner zones 185, 187 and 188.

Generally, the width of the various balling zones and reroll zone 189will be related to the height of rings 181, 182 and 183 as otherwise oneor more of these zones will becomeoverloaded and balling conditions andresults will be poor.

Balling vessel 190 shown in FIGURE 16 is a shallow, generallycylindrical container which is open at one end and is closed at theother by endwall 191, side wall 192 being welded to end wall 191 so thatthe vessel is essentially water-tight. Three concentric radiallydisposed and axially spaced annular ribs 193, 194, and 195 are welded tothe side wall 192 of the vessel to provide four separate annular zonesfor the agglomerating process of this invention. A green ball nucleatingzone 197 is provided in the inner part of vessel 192, being divided byend wall 191 and ring 193. Fine moist material contained in zone 197 isagglomerated through the rotary motion of vessel 190 as it is driven onits axis at an angle to the horizontal as illustrated with the resultsthat nuclei of green balls and small green balls are produced. Theproducts'of zone 197 are displaced from that zone by the introduction ofadditional quantities of material thereinto and these products arecollected in balling zone 198 defined by rings 193 and 194. Displacementof larger green ball products from zone 198 into zone 199 between rings194 and 195 likewise occurs as additional material isdelivered into zone198. A reroll zone 200 disposed outwardly of ring 195 receives ballproducts discharged from zone 199 and in turn discharges reroll ballproducts by the displacement material, these products emerging fromvessel 190 over the lip of side wall 192.

As the drawings show,-certain relationships exist between the dimensionsof the balling zones or troughs and the side walls of theseveral-vessels. In general, the vertical depth of each balling zone ortrough, or of the steps or ribs between adjacent zones or troughs, asmeasured at the lower segment of the vessel when it is in its rotatingposition, is less than the width of the zone or trough and is less thanhalf of the axial height of the side wall of the vessel. See troughs 49and 50 and rib 48 of FIG. 1, troughs 70 and 71 and ribs 73 of FIG. 4,and troughs 107, and 111 and ribs and 116 of FIGS. 7 to 10, andcorresponding parts of FIGS. 11 to 16, inclusive.

The purpose of the flow sheet of FIGURE 1 is to indicate the use of thepresent method and apparatus in the processing of finely-divided oreconcentrates and the relation of this invention to other phases of oreprocessing. A further purpose of this diagram is to indicatealternatives withinthis invention whereby two or more balling discs maybeused to produce the ball compact or where a single disc is employedfor this purpose as illustrated in the drawings above described. 7 Incarrying out the method of this invention in the flow sheet of FIGURE 1,the ore filter cake of 8% to 11% moisture content is mixed with asuitable quantity of bentonite or limestone or other similar additivematerial and then delivered into the agglomerating apparatus whereinwater is delivered as a spray in sufficient quantity to promoteagglomeration of the fine material. Preferably, this operation iscarried out continuously whether apparatus of the type illustrated inFIGURE 2 or that exemplified in FIGURES 3 and 7 are employed, andagglomerating is likewise carried out continuously as the agglomeratingvessel is revolved on its axis at a uniform rate. However, it iscontemplated by the present invention that the delivery of feed materialinto the agglomerating vessel may be carried on intermittently, and theintroduction of water into the vessel may likewise be discontinuouswhere itis desired to maintain a close control over the agglomeratingconditions and the rate of discharge of finished 'agglomerates is not tobe constant. Since, as indicated above, the ultimate size of theagglomerates is a function of the slope of the agglomerating vessel, theposition of the agglomerating'vessel is adjusted at the outset accordingto the size of the agglomerate product desired. In the preferredpractice, as in the use of the device of FIGURE 4, the slope of theagglomerating vessel may be changed at intervals during operation by wayof controlling the product size and the agglomerating conditions throughthe vessels in the course of their processing in the method of thisinvention.

It is preferable at the outset as well as throughout the period ofoperation of this invention to maintain a measure of controlover themoisture content of the feed material, and it is desirable that thefinely-divided feed be of substantially uniform moisture content withinthe range of 8% to 11%, as indicated above, as we have found that ironore fines of moisture in that range are capable of adhering to a metalsurface so as to provide a thin layer or coating on which small seedsand agglomerates may roll to produce growth through a snowballingefiect. It happens that this snowballing tendency is most marked whenthese fine materials exhibit the greatest tendency toward adherence andcoating on the agglomerating vessel wall. Adjustments in the moisturecontent to produce the ideal agglomerating condition may be made byintermittently or continuously delivering water into the agglomeratingvessel in contact with the fines in process, and this may be considereda step in the present method. As the agglomerating vessel is rotated onits axis and the coating of finely-divided ore and additives inadmixture is formed on the vessel walls, the step of trimming andconditioning this layer is carried out, preferably continuou'sly, sothat agglomeration is promoted. Thus, the layer or coating of fines issubjected to the action of a scraper bar which may be of the stationaryor the oscillating type and which serves to limit the thickness of thelayer of coating, removing excess fines preferably without producing anysort of polishing effect on the coating. Again, in analogy tosnowballing the best kind of coating surface for accretion ofagglomerates is one which will readily adhere to the agglomeratesthemselves with the result that part of the coating is lifted andcarried away as the agglomerates travel across the surface of thecoating in movement generated by the rotation of the agglomeratingvessel.

Intermittently or continuously depending upon the rate and continuity offeeding of fine material into the agglomerating vessel, agglomerates ofa predetermined size are separated and removed from the primaryagglomerating chamber of the vessel. In the operation of the apparatusof FIGURE 2, this step of the method involves carrying the thusdischarged agglomerates from a first vessel to a second vessel bysuitable means such as the conveyor 20. By contrast, this step in theoperation of the FIGURE 3 apparatus, for example, involves only therolling of the agglomerates over the lip of the wall defining the inneror primary agglomerating chamber of vessel 42 and the catching of thethus discharged agglomerates in the reroll ring 43. In either instance,however, the separation of the agglomerates from the small agglomeratesand seeds and/ or fines is the result of a clasification which takesplace in the primary vessel or chamber due to the action of theapparatus of this invention whereby a consolidated trickling phenomenonis induced by agitation and tumbling motions. The smaller fiocs or seedsgravitate through the layers of larger seeds or agglomerates so that aStratified arrangement of sizes diminishing in diameter as the layersare oriented from the surface downward is established. Additional feedresults in the uppermost layer being displaced from the primary vesselor chamber, while the other layers are retained therein. In commercialoperations, however, this classification and separation are not perfect,and there is a tendency for relatively small quantities in the betterpractice to carry over in discharge into the secondary vessel or chamberwith the intended agglomerate discharge.

Actually, in carrying out the method of this invention, advantage istaken of the fact that this tendency exists to a marked degree. Thus, inrerolling the agglomerates to produce agglomerates of the ultimatedesired size, it is not necessary to provide additional means fordelivering finely-divided material, feed or other forms of fines intothe secondary zone. At the same time, however, we prefer to carry out aseparation and removal of undersize agglomerates from the secondary zoneand this may be accomplished continuously or intermittently according tothe apparatus employed and the desires of the operator. As shown inFIGURE 5, scraper bar 101 performs this function automatically andwhenever necessary, but there are other ways in which this step can becarried out and this result obtained, as those skilled in the art willunderstand. The object, in any event, is to prevent build up ofexcessive and undesirable quantities of undersize agglom- 14' erates inthe secondary zone where they could impair the production of theultimate desired agglomerate and could also find their way into thefinal product.

' When the agglomerates reach the ultimate desired size in the secondaryzone, they are separated and removed in accordance with this inventionto a point of storage or apparatus for firing them or they may bererolled with solid finely-divided fuel as described above to provide afuel coating to aid in the firing operation. This rerolling ispreferably carried out continuously in a third zone in the form of asecond or a third agglomerating vessel, or more suitably in a secondreroll ring, as shown in FIG. 2. However, in either case, we have foundthat it is not usually necessary to provide for introduction ofadditional moisture, the agglomerates discharged from the secondary zonehaving sufiicient moisture in their surfaces to cause accretion andsecure binding of substantially dry coal or coke breeze particles toform a continuous coating on the agglomerates.

As a final step, the agglomerates bearing a coating of fuel of desireddegree of continuity and thickness are discharged from the third zoneand in the better practice this step will be carried out essentiallycontinuously and in generally the manner set out in relation to theseparating and removal steps described in detail above.

Although we have used various devices of this invention and made carefulobservations and tests and many detailed studies of the motions andflows of the materials in these vessels in carrying out our presentmethod, we are not certain what take place in this unique agglomeratingoperation. We have, however, developed a theory to explain the resultswhich we have obtained and without limiting our claims to this inventionin any way, we offer this theory by way of aiding others skilled in theart to understand this invention.

In accordance with our theory, it may first be assumed, for purposes ofillustration, that instead of a mixture of moist finely-divided ore andgreen ball nuclei and green balls of various sizes and of equal specificgravity, the vessel of FIGURE 11 is loaded with marbles graduated as tosize with the smallest being located in the innermost portion of vesseland the largest in the reroll zone 132. As vessel 105 is rotated on itsaxis in a clockwise direction at a constant rate of about 15 revolutionsper minutes, the marbles in the separate zones are carried upwardly toroll back under gravitational force and are carried up again in acascading action. This is a stable system in which there is essentiallyno migration of marbles between the separate zones and as long as thereis no break-down of the marbles due to the rolling action, there will beno change in the disposition of the system. However, if it is assumedthat marbles of the small size or the more finely-divided materials arecharged into zone 107, there will be displacement of the larger bodiesfrom Zone 107 and as this charging continues, displacement of largerbodies from each of the outer zones begins and continues. A certainamount of the finer material in each instance is displaced from theinner zones. However, a counterfiow of undersize material takes place asthis material is carried upwardly by the centrifugal force in1-. partedby vessel 105 until gravitational force draws the undersize materialtoward the inner zones of the vessel. If it is further assumed thatfeeding of the small size marbles or fine material is continued for along period, it is seen that theoretically this will result in theeventual displacement of essentially all the original marble charge fromzones 107, 110 and 111. Ultimately, flooding of reroll Zone 132 by thefiner material will, likewise, result in the elimination ofsubstantially all the original marble charge from the vessel.

If, in addition to the above assumptions, it is assumed that accretionof the marbles of various sizes occurs in zones 107, 110, and 111, itwill be understood that the result just described will not be obtained,providing such accretion takes place at a rate corresponding to the rateof charge of fine material into zone 107 and the rate of discharge ofball products from zones 111 and 132. This, of course, implies a netaccretion rate where there is any tendency for degradation of the ballproducts in the vessel as it can be imagined that under certainconditions, ball formation and ball breakage could take place at thesame rate with the result that no finished ball products would beobtained through the operation of the vessel. Balance between this netaccretion rate and the in-feed or charge rate to the vessel will mean,among other things, that outward flow of undersize material into zones110 and 111 will be greater in volume than the counterflow from thesezones back toward zone 1107, this undersize material being consumed inball accretion in these outer zones. It will also mean that accretion oflarger balls in zone 110 or 111 will be promoted, it being ourobservation that, surprisingly, the tendency is not for these undersizematerials and fines to produce new small balls or nuclei but to promotegrowth of the larger ones.

This application is a division of our copending application Serial No.580,423, filed February 15, 1956.

Having thus described the present invention so that others skilled inthe art may be better able to understand and practice the same, we statethat what we desire to secure by Letters Patent is defined in what isclaimed.

What is claimed is:

1. A pelletizing apparatus adapted to form pellets of powdered materialhaving its particles in an adhesive condition, the apparatus comprisinga vessel having a substantially flat bottom and substantially circularconfining wall members rising from the bottom portion, and having itsinner surface shaped to form a plurality of annular coaxial trough-likeportions of different diameter, the smaller being adjacent the flatbottom portion, said trough-like portions being separated by annularridge portions, means for mounting the vessel to rotate on an axis at anacute angle to the horizontal, and means for feeding moistened powderedmaterial to be pelletized to the vessel while rotating.

2. The apparatus described in claim 1 in Whch the plurality oftrough-like portions have a vertical depth at the lower segment when thevessel is in rotating position of substantially less than one-half ofthe axial height of the side Wall of the vessel.

3. The combination of elements set forth in claim 1 in which each of thetrough-like portions has a vertical depth at the lower segment when thevessel is in rotating position of substantially less than the axiallength of said portion.

4. The combination of elements set forth in claim 1 in which each of thetrough-like portions'has an axial length of between about 6" and about 9/2".

5. The combination of elements set forth in claim 1 in which at leastthe smaller of the trough-like portions has an axial length of betweenabout 6" and about 9 /2".

6. The combination of elements set forth in claim 1 in which scrapermeans are spaced from the bottom surface of the disc to form asubstantially uniform depth of the material moving with the discsurface.

7. The combination of elements set forth in claim 1 in which there is afiller in the corner like space between the base and side wall of atleast the smaller trough-like portion.

8. The combination of elements set forth in claim 1 in which theoutermost annular ridge portion has an axially extending barrier toprevent the return of balls from the outermost trough-like portion toother trough-like portions.

9. The combination of elements set forth in claim 1 in Which at leastthe smaller trough-like portion has a depth as measured axially of thevessel of between about 6 and about 9 /2 and in which the acute angle isbetween about 20 and about to the horizontal.

10. A pelletizing apparatus adapted to form pellets of powdered materialcomprising a vessel having a substantially fiat bottom and asubstantially circular confining wall rising from said bottom anddefining at least two annular coaxial trough-like portions of differentdiameter, the smaller being adjacent to the flat bottom and having adepth measured axially of the vessel of between about 6" and about 9/2", an annular ridge separating said trough-like portions, means formounting the vessel to rotate on an axis disposed at an angle of betweenabout 20 and about 70 to the horizontal and means for rotating thevessel.

11. A process of mixing and blending of finely divided solids andeffecting the aggregation thereof into components of particles andpellets, comprising the steps of causing the material to cascade androll upon itself in a thin sloping flat body of the material conformingat its under side substantially to a sloping plane, forming segments andportions of the material of varying depth and of different length incurving zones causing the formation of nuclei, continuing the motion ofrolling the material upon itself in sloping plane formation whileeffecting cascading and forming pellets by accretion upon the nuclei andof individually increasing size, progressively moving the larger pelletsso formed outwardly from the zone of the sloping plane of material fromone curving path to another, gathering the nuclei and pellets intosegmental concentric moving bodies of radially narrow dimension and of adepth limited to such dimension as to prevent sliding in a mass andcontinuing the rolling and fallmg action to move the formed largerpellets outwardly to another concentric moving narrow mass, whiledelivering larger formed pellets from the outer portion thereof and atthe same time returning the smaller pellets and particles upwardly alongthe plane of the sloping thin revolving mass.

References Cited in the file of this patent UNITED STATES PATENTS312,041 Upjohn Feb. 10, 1885 1,239,221 Rodrnan Sept. 4, 1917 1,537,348Grossmann May 12, 1925 2,411,873 Firth Dec. 3, 1946 2,543,898 De VaneyMay 6, 1951 2,709,833 Wiklund June 7, 1955 2,726,959 Lushbough et alDec. 13, 1955 2,818,601 Argarwal Ian. 7, 1958 2,834,043 Haley et al. May13, 1958 2,860,598 Loesche Nov. 18, 1958 FOREIGN PATENTS 502,233 CanadaMay 11, 1954 915,072 Germany July 16, 1954

1. A PELLETIZING APPARATUS ADAPTED TO FOR PELLETS OF POWDERED MATERIALHAVING ITS PARTICLES IN AN ADHESIVE CONDITION, THE APPARATUS COMPRISINGA VESSEL HAVING A SUBSTANTIALLY FLAT BOTTOM AND SUBSTANTIALLY CIRCULARCONFINING WALL MEMBERS RISING FROM THE BOTTOM PORTION, AND HAVING ITSINNER SURFACE SHAPED TO FORM A PLURALITY OF ANNULAR COAXIAL TROUGH-LIKEPORTIONS OF DIFFERENT DIAMETER, THE SMALLER BEING ADJACENT THE FLATBOTTOM PORTION, SAID TROUGH-LIKE PORTIONS BEING SEPARATED BY ANNULARRIDGE PORTIONS, MEANS FOR MOUNTING THE VESSEL TO ROTATE ON AN AXIS AT ANACUATE ANGLE TO THE HORIZONTAL, AND MEANS FOR FEED-